A common-source amplifier is shown below. The MOSFET parameters are k'n = 2mA/V2, VT = 0.8 V. The amplifier is biased with a source VDD = 5 V, and resistors RD = 4 kohm, RS = 1 kohm, RG1 = 225 kohm, RG2 = 175 kohm, Vov = 0.75 V (a) Calculate the drain current ID. Recall the formula for a MOSFET in saturation: ID = 1/2k'n(VGS - VT)2 (b) Obtain the MOSFET voltage vDS. (c) Using small-signal analysis, obtain the voltage gain vo/vi for RL = 12 kohm. Assume ro = 100 kohm, gm = 1 mA/V.
A source follower (Common Drain Amplifier), shown below, is required to connect a high-resistance source to a load whose resistance RL is 2 kohm (a) What is the maximum output resistance Ro that the source follower must have if the gain Av value = 0.85 V/V ? (b) Find the value of gm. (c) If the MOSFET has kn = 10 mA/V2, at what current In must it be biased? (d) At what overdrive voltage Vov is the MOSFET operating?